Description: (from applicant's Abstract) Patients with Chronic Obstructive Pulmonary Disease (COPD) have risk factors for the development of osteoporosis including: heavy smoking history, corticosteroid use, sedentary life style. Few studies have examined the incidence of bone loss in these patients and no studies have compared bone mass in men and women with COPD. The purpose of this study is to examine the relationship of variables that potentially influence bone mass with current bone compared between men and women with COPD, and healthy men and healthy women. The sample will consist of 45 patients with COPD, and 45 healthy subjects. In order to control for the effects of smoking history vs. disease state on BMD, the healthy group will be divided into those with a significant smoking history (>20 pack-years) versus those with minimal or no smoking history (<20 pack years). Bone mineral density will be measured using dual energy x-ray absorptiometry (DXA) at the following sites: PA lumbar spine, proximal femur, and whole body. Variables potentially influencing BMD will be measured: 1. calcium and ethanol intake as measured by the Bloc' '98 Food Frequency Questionnaire, historical and current physical activity as measured by the Historical Liesur Time Activity Questionnaire and the Physical Activity Scale for the Elderly respectively, cumulative smoking: history as measured by the number of pack-years, gonadal hormones as measured by serum testosterone and serum estradiol levels, corticosteroid use as measured by clinical questionnaire, body mass as measured by body weigh and whole body DXA scan. Statistical analysis will include: 1. univariate linear regression with lumbar spine BMI and proximal femur BMD as dependent variables and smoking history, disease state, calcium intake, ethanol intake physical activity, gonadal hormone levels, corticosteroid use, body mass as independent variables; and 2. analysis of variance with lumbar spine BMD and proximal femur BMD as dependent variables. Results of this study will provide improved understanding of the nature of bone loss in COPD patients.